Effects of controlled progressive hypotension on some spinal reflexes in the cat

Abstract

In the unanesthetized spinal cat at normotensive levels the crossed extensor reflex appeared considerably more variable than the patellar reflex. Both reflexes failed progressively as blood pressure was lowered but became hyperexcitable and were accompanied by convulsions at mean arterial pressures of 20–40 mm Hg. The crossed extensor reflex was more affected by hypotension than the patellar reflex. These reflexes disappeared under continued severe hypotension and recovered upon restoration of blood pressure to normal. Supplementary observations on spinal and intact cats under chloralose anesthesia indicated that the patellar reflex was more affected at less severe hypotensive levels in animals with an intact cerebrospinal axis.